1. Field of the Invention
This invention relates generally to apparatus and method for conjuncting and separating density differentiated components from a moving carrier liquid. More particularly, this invention concerns method and apparatus for use in a conventional flow-through separating tank.
2. Description of the Prior Art
Various devices are known for purifying liquids by mechanically separating undesirable components having densities different from that of the desired carrier liquid. This purification process involves both conjuncting and separating particles of the undesirable components. The conjunction operation includes coalescing and flocculating undesirable component particles to achieve particle sizes that are then susceptible to separation by settling or rising out of the carrier liquid as governed by Stokes' law.
Devices that perform the discrete conjuncting and separating functions are known. Conventional conjuncting devices include motorized paddles, impellers that agitate the carrier liquid, or stationary baffles and pipes through which the carrier liquid flows. By increasing the shear, i.e., changing the velocity with respect to distance, in the liquid to be treated, these devices cause suspended components to collide because of their differential velocities, leading to coalescence and flocculation of the component particles.
Clarifiers and parallel plate devices are examples of known separating apparatus. These devices utilize an increased effective settling or rising area and the principle of overflow rate to remove carrier liquid components having a settling or rising velocity parallel to the gravity force vector.
Early parallel plate devices included a stack of substantially parallel plates defining passages therebetween through which the liquid to be treated was flowed. As shown by U.S. Pat. No. 1,458,805 to Christensen, the stacked plates would be sloped and the liquid to be treated would be introduced from the upper or lower side of the plates. Heavy solids would thus flow downward along the plate surfaces, while the clear, lighter liquid would float upward.
Various modifications to the basic parallel plate concept have subsequently been made. For example, the use of corrugated plates, instead of smooth plates, has been suggested. U.S. Pat. No. 3,346,122 to Cornelissen discloses the use of corrugated plates. It has also been suggested that the flow of the carrier liquid should be transverse to rather than in line with the plates, as shown by U.S. Pat. No. 1,732,386 to Sprockhoff. Further examples of such devices are shown in U.S. Pat. No. 1,946,414 to Schmid, U.S. Pat. No. 386,114 to Donahue, and U.S. Pat. No. 3,837,501 to Pielkenrood. In all of the foregoing configurations, the inclination of the parallel plates directs the separated components to the boundaries of the plate pack for recovery.
All known systems for separating components from a carrier liquid are designed based on differential settling velocities of the discrete component particles. These settling velocities are determined by density differences between the component particles and the carrier liquid, carrier liquid viscosity, and particle diameter. Consideration of these factors results in a design which utilizes parallel plates to develop a uniform carrier liquid velocity distribution with minimum shear.
The components to be separated have a normal distribution of particle sizes and densities about some mean value. Conventional parallel plate systems separate each particle individually, independent of all other particles. This results in non-uniform performance of these parallel plate systems because of the various densities and sizes of the particles to be separated.
In addition to the disadvantage of non-uniform operation, conventional parallel plate devices are inadequate to conjunct component particles for subsequent settling or rising separation from the carrier liquid. Thus, a separate conjuncting device or chemical treatment is required to produce adequate particle size.